The present invention relates to an adjusting mechanism for a neck aligner for use in a stringed instrument.
As is known, a neck of a stringed instrument inevitably is deformed by ordinary warpage due to tension of strings extended over the stringed instrument in a mode that a head part of the neck is drawn toward the side of a bridge device.
Therefore, an aligner is provided in the neck of the stringed instrument to straighten the neck to compensate for such ordinary bending deformation. This aligner has a resilient rod member having a high degree of rigidity. Such rod member is inserted into the neck as a truss rod and is adapted to apply a straightening force to the instrument in a direction opposite to the direction of ordinary bending of the neck by reducing the length of the truss rod when ordinary bending of the neck occurs.
The aligner as described above employs two rod members, as disclosed in Japanese Patent Application Disclosure Gazette (TOKUKAI) Nos. HEI. 1-231098 and HEI. 1-234898, or one rod member, as disclosed in Japanese Patent Application Disclosure Gazette (TOKUKAI) No. HEI. 1-213697 and Japanese Utility Model Application Disclosure Gazette (JITSUKAI) No. HEI. 3-33488.
The above-described aligner is provided in the neck with an adjusting mechanism for reducing the length of the truss rod inserted into the neck. The adjusting mechanism can be externally operated and is arranged in a hollow space formed in a head part of the neck, as disclosed in the above Japanese Patent Application Disclosure Gazette No. HEI. 1-234898 and Japanese Utility Model Application Disclosure Gazette No. HEI. 3-33488, or arranged at a body side coupling portion of the neck, as disclosed in Japanese Utility Model Application Disclosure Gazette No. SHO. 58-38192. Adjustment is achieved with such adjusting mechanisms by directly inserting an adjusting tool to the end of the truss rod through the hollow space of the head part of the neck or the internal hollow space of the body.
However, there are various types of stringed instruments in which an internal hollow space cannot be formed in the body, or the head is not provided with a hollow space for the appearance of the neck as a fender type guitar. In the case of these types of stringed instruments, the length of the truss rod cannot be adjusted while the neck is attached to the body.
Stringed instruments for which the truss rod is adjusted by inserting a wrench through a hollow space of the head part of the neck or a hollow space formed in the body are disadvantageous in that handling of the wrench is limited by the extended strings. Therefore, adjusting operations are difficult since adjustment must be carried out by inserting the wrench through tuned strings.
Therefore, an adjusting mechanism which makes it possible to adjust the length of the truss rod in the neck from the side of the neck has been proposed. Such mechanism is adapted so that a worm gear mechanism is coupled to an end part of the truss rod to actuate the truss rod, as disclosed in Japanese Utility Model Application Disclosure Gazette Nos. SHO. 54-94220 and HEI. 3-20392. The adjusting mechanism using the above worm gear mechanism is constructed so that a threaded part formed at the-end of the truss rod is meshed with a worm wheel. The worm is rotated by an external operation, while the worm wheel is kept meshed with the worm to move the threaded part of the truss rod forwardly and backwardly in an axial direction, thereby changing the length of the truss rod.
As regards the adjusting mechanism which employs such worm mechanism as described above, there is a problem that it is necessary to reduce the pitch of the worm wheel to accurately adjust the length of the truss rod. However, if the pitch of the worm wheel is made small, the adjusting mechanism cannot withstand a resilient force to be applied during adjustment of the length of the truss rod and is not applicable to practical use. Moreover, external operation of the worm wheel cannot be carried out lightly and smoothly, since the worm wheel is internally meshed with the end part of the truss rod, and adjustment of the length of the truss rod is doubly decelerated by the internal and external threads of the worm wheel.